Computer chip packages comprise microchips embedded in ceramic pin grid arrays ("PGA"). Pins extend out of the PGA which carry signals to and from the microchip. The pins are inserted into a chip socket in order to operate the microchip. Microchips generate substantial amounts of heat which can lead to malfunction from cycling problems. In order to reduce the heat in microchips, heat sinks have been devised to carry heat away from the microchip and from the chip package. Typically, these devices are sets of fins or lances attached by an epoxy adhesive to the back of the microchip package. The epoxy adhesive must be carefully chosen such that chip breakage does not result due to a mismatch in thermal expansion rates of the package and the epoxy. Once the heat sink is thus affixed to the chip, it is not easily removed, particularly since the package is a delicate device subject to destruction if stressed. Since the identifying marks of the chip are located on the back of the package, once the sink is attached by the epoxy, the chip becomes virtually unidentifiable. This makes servicing the overall system more difficult as a separate record of the chip identities must be maintained. Furthermore, resale of used chips becomes impracticable.
In an attempt to overcome these problems, heat sinks have been developed that mechanically engage the chip package or the chip socket. The Thermalloy PGA E-Z Mount.TM. device comprises a rectangular frame in which the PGA sits. In this device, the pins of the PGA run through holes in the frame, keeping the frame in place. Alternatively, two shoes can be attached to opposite sides of the PGA by slipping the pins into holes in the shoes. A spring is attached to a heat sink. The spring then attaches to the frame, holding the heat sink in place against the chip package. There are several drawbacks to these designs. First of all, these devices comprise several parts. In addition, the frame or shoes must be attached before the chip package is mounted onto the chip socket. Finally, the heat sinks for use with this device comprise fins protruding out from the top of the sink, requiring more space.
The Thermalloy 2311 Series Integrated Circuit Heat Sink is a screw-on heat sink. The chip package is mounted on the chip socket. A latch cover is attached to the socket, covering the package. The sink screws into a socket in the latch cover such that the sink is disposed above the chip package.
The present invention relates to a low-profile heat sink (or "sink") for a computer chip package that can be easily mounted and easily removed without harming the microchip or the pin grid array. The sink of this invention permits the package to be mounted on and dismounted from the chip socket while the sink is attached. In addition, the sink can be mounted and dismounted from the package whether or not the package is mounted in the socket.